The present invention relates generally to a method for joining metals without welding and, more particularly, to a method for joining two components formed of sheet material.
Spot welding is commonly used to join two relatively thin metal components. Steel components are typically galvanized for use in the automotive industry. Galvanization of steel components presents special processing techniques if spot welding is desired to join the component to another component. The galvanized coating layer must be burned off during spot welding to form a welded joint. Galvanized coating when burnt emits noxious fumes which must be vented in a manufacturing facility. Consequently, the spot welding must be performed under special hoods to draw the fumes out of the facility. Galvanized material also builds up on the tip of the spot welding machine. Thus the welding tip must be cleaned frequently. Both adding a hood to the plant and cleaning the tip of the welding machine increase the cost of spot welding of galvanized materials.
Another disadvantage of spot welding is that the process must be performed on two similar composition materials. If the two materials have different compositions, spot welding may not be suitable.
Punching or otherwise mechanically manipulating two thin metal materials is old in the art. Typically the metals are bent in such a manner so as to prevent them from pulling apart. By using mechanical deformation, the galvanized material does not have to be removed in a localized area for joining. By mechanically deforming the material, the above-mentioned drawbacks to spot welding are eliminated.
An apparatus for joining sheet material has been developed by BTM Corporation of Marysville, Mich. Generally, the process places the two sheet materials adjacent to each other. The sheet materials are drawn together and slightly deformed so that the two materials are joined. Essentially the top material is drawn into the bottom material. When mechanically deformed, the bottom material holds the top material in place. One problem with such a method for joining sheet material is that when such a process is used for joining dissimilar thickness materials, a weak joint may result. Typically, it is not recommended to use such a process when a relatively thin material is drawn into a relatively thick material.
In many instances on automotive vehicles various gauge materials are used on components to be joined. Such is the case for glass guide channels that are used within the door of an automotive vehicle and the brackets that hold them within the door. A glass guide channel generally is a relatively thin U-shaped channel made from formed sheet steel. The brackets that hold the channels in place are generally several times thicker than the channels due to the forces they encounter during operation of the window. It is desirable to draw the U-shaped channel into the bracket for a mechanical joint. However, because the forces are great, the relatively thin material is easily pulled from the thick material causing the joint to fail.